void stringTest() {
  /*
  var s1 = 'Single quotes work well for string literals.';
  var s2 = "Double quotes work just as well.";
  var s3 = 'It\'s easy to escape the string delimiter.';
  var s4 = "It's even easier to use the other delimiter.";*/

  // String 类型可以使用 + 操作：
  var s1 = 'String ' 'concatenation'
          " works even over line breaks.";
  print(s1);
  assert(s1 == 'String concatenation works even over '
              'line breaks.');

  var s2 = 'The + operator '
          + 'works, as well.';
  print(s2);
  assert(s2 == 'The + operator works, as well.');



  // 可以使用三个‘ 或“来定义多行的String 类型。(这点和Python 语言类似。)
  var s3 = '''
  You can create
  multi-line strings like this one.
  ''';
  print(s3);

  var s4 = """This is also a
  multi-line string.""";
  print(s4);



  // 可以使用r 来修饰String类型，表 表明是“raw” 类型字符串：
  var sr = r"In a raw string, even \n isn't special.";
  print(sr);



  // String 类型是 compile-time 的常量。 可以在编译是才给String类型赋值。
  // These work in a const string.
  const aConstNum = 0;
  const aConstBool = true;
  const aConstString = 'a constant string';

  const validConstString = '$aConstNum $aConstBool $aConstString';
  print(validConstString);

  // These do NOT work in a const string.
  /*
  var aNum = 0;
  var aBool = true;
  var aString = 'a string';
  const aConstList = const [1, 2, 3];
  const invalidConstString = '$aNum $aBool $aString $aConstList';
  print(invalidConstString);*/
}